Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended								12 Months Ended
	Aug. 31, 2013	Apr. 30, 2016	Jan. 30, 2016	Oct. 31, 2015	Aug. 01, 2015	Apr. 25, 2015	Jan. 24, 2015	Oct. 25, 2014	Jul. 26, 2014	Apr. 30, 2016	Apr. 25, 2015	Apr. 26, 2014
Business Acquisition [Line Items]
Goodwill		$ 816,592,000				$ 299,924,000				$ 816,592,000	$ 299,924,000
Net sales		1,453,770,000	$ 1,400,853,000	$ 1,389,210,000	$ 1,142,870,000	1,035,061,000	$ 958,628,000	$ 978,220,000	$ 938,956,000	5,386,703,000	3,910,865,000	$ 3,585,141,000
Operating income		106,344,000	95,729,000	83,463,000	62,177,000	$ 89,073,000	$ 77,377,000	$ 72,140,000	$ 65,996,000	347,713,000	$ 304,586,000	293,726,000
Tax impact of repatriation of foreign earnings					11,800,000					12,300,000
Animal Health International [Member]
Business Acquisition [Line Items]
Business acquisition cash paid					1,106,583,000
Identifiable net assets acquired					588,618,000
Deferred tax liability					180,145,000
Goodwill					517,965,000
Goodwill recognized, deductible for income tax purpose					0
Deferred taxes recorded related to goodwill					0
Net sales										1,396,118,000
Operating income		15,034,000	9,827,000	10,716,000	1,653,000					37,230,000
Amortization expense related to identifiable intangible assets										28,112,000
Net sales		$ 403,580,000	$ 406,588,000	$ 414,028,000	171,922,000
Patterson and Animal Health International, Inc. [Member]
Business Acquisition [Line Items]
Tax impact of repatriation of foreign earnings										$ 12,300,000
National Veterinary Services Limited (NVS) [Member]
Business Acquisition [Line Items]
Business acquisition cash paid	$ 142,693,000
Net sales												$ 419,340,000
Term Loan [Member] | Animal Health International [Member]
Business Acquisition [Line Items]
Unsecured term loan					1,000,000,000
Unsecured Revolving Line of Credit [Member] | Animal Health International [Member]
Business Acquisition [Line Items]
Maximum borrowing capacity					$ 500,000,000